Experimental study on the feasibility of using liquid-assisted processing in fabrication of Mo-Si-B alloys

In this work, we used a sessile drop experiment to assess a feasibility of novel processing design engaging liquid-phase assisted fabrication of multi-phase materials from Mo-Si-B system. For this purpose, binary eutectic silicon-boron alloy (Si-3.2B wt%) was subjected to contact heating with polycrystalline molybdenum substrate at temperature up to 1385 °C. It was in-situ observed that molten Si-3.2B alloy wets and rapidly spreads over the Mo surface. After the high temperature test, the solidified couple was subjected to structural characterization by scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy and X-ray diffraction methods. The obtained results revealed that the direct interaction between examined materials under applied testing conditions results in the reactively formed product layer having a thickness of ~80 µm. The following structural features were recognized starting from the surface side: (I) the main product layer composed of columnar-like MoSi2 phase and Mo5Si3 phase; (II) an intermediate layer made of MoB and Mo5SiB2 phases. Although these results give the first indication for designing a novel liquid-assisted fabrication method of Mo-Si-B materials, an existence of porosity in the product layer clearly suggests that a further optimization of the process parameters is necessary.